This invention relates to a process for preparing hydroperoxides from polyalkylbenzenes in the presence of sulfolane.
The use of sulfolane to increase the rate of formation of hydroperoxides from alkyl- and polyalkylbenzenes is disclosed in U.S. Pat. No. 3,524,888. This patent also discloses that when an alkylbenzene like toluene, ethylbenzene, cumene or a polyalkylbenzene like ortho-xylene, 1,3,5-trimethylbenzene or 4-isopropyl-o-xylene are oxidized in the presence of sulfolane a homogeneous solution is formed. The homogeneous solution enables better contact of the reactants and aids in the reaction and permits ready separation of the hydroperoxide products. When 5-isopropyl-m-xylene (3,5-dimethylcumene) was oxidized in the presence of sulfolane there was no apparent increase in the rate of formation of hydroperoxides. The lack of such an increase occurred because of the immiscibility of 5-isopropyl-m-xylene in sulfolane preventing the formation of a homogeneous reaction mixture.
It is well known to produce resorcinol or hydroquinone from meta-diisopropylbenzene or para-diisopropylbenzene, respectively, by oxidation to produce the dihydroperoxide which by cleavage with strong acid catalysts is converted to resorcinol or hydroquinone and acetone. The oxidation of both alkyl groups of the meta-, or para-diisopropylbenzene (DIPB) is readily inhibited and only partial oxidation can be achieved without considerable loss of efficiency and rate of oxidation. DIPB is oxidized first to the mono-hydroperoxide which is then further oxidized to the dihydroperoxide. In actual practice the reaction is stopped at a high mono-/dihydroperoxide ratio to reduce the formation of the numerous undesirable by-products otherwise formed in the oxidation of DIPB, such as carbinols, ketones, and carbinol-hydroperoxides which interfere with the oxidation. Increasing the temperature will increase the rate of reaction but it will also increase the formation of by-products. Therefore, a balanced operation requires relatively moderate temperatures of around 80.degree.-90.degree. C. Even at these conditions with a low rate of reaction the reaction eventually stops due to the inhibition of the oxidation by-products, and the ratio of DIPB-mono-/-dihydroperoxide is high.
It would be most desirable to increase the rate of reaction to hydroperoxides and to increase the conversion to DIPB-dihydroperoxide by oxidizing the DIPB in the presence of sulfolane. Unfortunately, the DIPB, as well as 5-isopropyl-m-xylene, and other polyalkylbenzenes, which have at least one alkyl group having three or more carbon atoms where one carbon atom is a tertiary carbon atom, including compounds such as 1,3,5-triisopropylbenzene, is immiscible with sulfolane. This immiscibility prevents the formation of a homogeneous reaction mixture and, therefore, also prevents the benefit of higher reaction rates in the production of hydroperoxides from the above-mentioned compounds.
It is an object of this invention to provide a process to enable the formation of a homogeneous reaction mixture when polyalkylbenzenes that are immiscible in sulfolane are oxidized in the presence of sulfolane to obtain an increased rate of reaction in the formation of hydroperoxides.